Apparatus for making well screen



Sept. 30', 1969 H. F. SMITH 3,469,609

APPARATUS FOR MAKING WELL SCREEN Filed July 11, 1967 7 Sheets-Sheet 1 Harm/w F 5mm,

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APPARATUS FOR MAKING WELL SCREEN Filed July 11, 1967 7 Sheets-Sheet 2 HOWARD E SM/TH, ZZT

A TTORNEYS Sept. 30, 1969 H. F. SMITH 3,469,609

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Filed July 11, 1967 APPARATUS FOR MAKING WELL SCREEN 7 Sheets-Sheet 4 .IIL

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APPARATUS FOR MAKING WELL SCREEN Filed July 11, 1967 7 Sheets-Sheet 5 HOWARD E 5mm HI I I INVbN'I OR ATTORNE Y5 Sept. 30, 1969 H. F. SMITH m 3,469,609

APPARATUS FOR MAKING WELL SCREEN Filed July 11, 1967 7 Sheets-Sheet 6 I N VEN TOR.

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INVENIOR.

BY v

4 r role/v22 rs United States Patent US. Cl. 140-112 4 Claims ABSTRACT OF THE DISCLOSURE The apparatus described makes well screen by mounting a perforated tube between the head stock and the tail stock of an engine lathe for rotation around its longitudinal axis. One end of a wire is anchored to the tube, or adjacent one end of the tube, to be wrapped around the tube as it is rotated. Rods may or may not be spaced around the outside of the tube to space the wire away from the tube. The wire is fed through rollers that are moved parallel to the tube by the lathe carriage to cause the wire to wrap around the tube in spaced helical coils. A welding machine having two electrode wheels is carried by the carriage to weld the wire to the tube or to the rods, if spacer rods are used. The welding electrode engages the wire as it is initially bent around the tube. If no rods are present the welding electrode continuously welds the wire to the tube, as the wire passes between the electrode and the tube. If spacer rods are used, the electrode welds the wire to each spacer rod as the wire and each rod passes between the electrode and the tube. The second electrode provides a ground connection for the welding current. It travels with the first electrode and is located to roll along the already welded wire a few coils from the welding electrode. The speed of travel of the carriage can be varied independently of the speed of rotation of the tube to allow the gage of the screen to be varied as desired. Two back-up rollers are provided, each being positioned on the other side of the tube from one of the electrodes. The back-up rollers move with the electrodes and equalize the lateral forces imposed on the tube by the electrodes.

This invention relates generally to apparatus for making well screens and, in particular, to apparatus for making well screens by wrapping a wire around a perforated mandrel in spaced helical coils.

In well screen of this type, the space between adjacent coils of wire is a measure of the gage of the screen. To keep adjacent coils of wire from moving together or apart in service, the Wire is either welded to the mandrel or laterally extending tabs are periodically bent out of the wire along its length to hold the coils apart. The mandrel can be a tube provided with a plurality of perforations, a plurality of spaced parallel rods arranged to outline a cylinder, or a combination of both the perforated tube and the rods. Where the rods are used, and the wire is to be welded to the mandrel, the practice is to weld the wire to each rod as the wire is wrapped 0n the rods. This was done heretofore by moving the rods longitudinally past a stationary wire feeding station, while rotating the rods to wrap the wire onto the rods in spaced helical coils. A welding electrode was positioned at the wire feeding station to weld the wire to each rod as the wire was wrapped on the rods. A stationary ground electrode, in contact with all of the rods, provided a return path for the welding current passing through each rod as the wire was welded to it.

When making screen in this manner, the working area required had to be at least twice the length of the screen being made. In addition, since each rod had to move longitudinally with respect to its ground electrode, it was 3,469,609 Patented Sept. 30, 1969 diflicult to maintain good electrical contact all of the time, which caused variations in the quality of the welds.

It is an object of this invention to provide apparatus for making a well screen that requires a working area that is considerably less than twice the length of the screen it produces.

It is a further object of this invention to provide appapatus for making a well screen in which the welding electrodes and wire feeding station move along the mandrel to reduce considerably the space required for the screen making apparatus.

It is a further object of this invention to provide such apparatus that has a welding electrode and a ground electrode which can automatically adjust to changes in the outside diameter of the mandrel to maintain uniform contact pressure with the wire and the mandrel around which it is being wrapped.

It is another object of this invention to provide apparatus for making a well screen that produces good, uniform welds between the mandrel and the wire that is wrapped around it.

It is a further object of this invention to provide appapatus that can wrap and weld wire to a perforated tube that is supported for rotation at its ends only.

It is another object of this invention to provide apparatus for making well screens that can produce screen of any desired gage.

These and other objects, advantages, and features of the invention will be apparent to those skilled in the art from a consideration of this specification, attached drawings, and appended claims.

The invention will now be described in connection with the attached drawings in which;

FIGURE 1 is a front side view in elevation of the preferred embodiment of the apparatus of this invention in the process of making a well screen;

FIGURE 2 is a cross sectional view of the apparatus of FIGURE 1 taken along line 2-2;

FIGURE 3 is a view taken along line 33 of FIG- URE 2;

FIGURE 4 is a sectional view along line 4-4 of FIG- URE 2;

FIGURE 5 is a sectional view along line 55 of FIG- URE 3;

FIGURE 6 is a sectional view along line 6-6 of FIG- URE 2;

FIGURE 7 is a sectional view along line 77 of FIG- URE 6;

FIGURE 8 is a cross sectional view showing wire being wrapped and welded on a mandrel;

FIGURE 9 is an enlarged view of the welding operation of FIGURE 8;

FIGURE 10 is an enlarged, fragmentary top view of the welding operation with the perforated tube of the mandrel in section;

FIGURE 11 is a view on an enlarged scale of the welding electrode and the wire as the welding operation begins;

FIGURE 12 illustrates how the mandrel is mounted in the apparatus for forming a well screen and the arrangement of the wire at the beginning of the well screen making operation;

FIGURE 13 illustrates the structure of a well screen where the wire is welded directly to a perforated tube, which forms the mandrel;

FIGURE 14 is an enlarged view of the welding of the wire directly to a perforated tube to form the screen of FIGURE 13; and

FIGURE 15 is a schematic illustration of the power transmission system of the apparatus that allows for the gage of the screen to be varied as desired.

The apparatus of this invention includes means for supporting an elongated cylindrical mandrel, having a plurality of openings throughwhich fluid can pass, for rotation around its longitudinal axis to cause wire having one end anchored to rotate with the mandrel to wrap itself on the mandrel.

As explained above, the mandrel for a well screen can be either a perforated tubular member, a plurality of spaced parallel rods arranged to outline a cylinder, or a combination of both the perforated tube and the rods. The apparatus shown in the drawings will be described in connection with making a well screen having a mandrel comprising a perforated tubular member around which are arranged a plurality of spaced parallel rods. To form the screen the wire is wrapped around the rods and welded'to each rod that the wire engages.

In the embodiment shown, engine lathe in FIGURE 1 is provided to rotate the mandrel on its longitudinal axis. The lathe includes chuck 11, which is rotated by head stock 12. One end of tubular member 13 is gripped by chuck 11 for rotation with the chuck. The other end of tubular member 13 is supported for rotation by dead center 14 of tail stock 15. The speed of rotation of tube 13 by chuck 11 is determined by the setting of the gear train in the head stock of the lathe in the conventional manner.

Carriage 16 is supported for movement parallel to the longitudinal axis of the tubular member by bed 17 of lathe. 10. The speed of movement of carriage 16 is determined by the speed of rotation of lead screw 18. The arrangement for rotating the lead screw in order to permit the apparatus to produce screen of any desired gage is described below.

In the embodiment shown, the mandrel upon which the wire is to be wound includes longitudinally extending rods 20 that serve to space the wire from perforations 13a in perforated tube 13. The rods extend parallel to the longitudinal axis of the tube and are equally spaced around the outside surface of the tube. The manner of holding the rods in place on the tube during the making of the screen is shown in FIGURE 12. The ends of the rods adjacent chuck 11 are held in place by split collar 21. The collar includes clamp portion 21a and sleeve portion 21b. The clamp portion anchors the collar in place on the tubular member to hold the rods against longitudinal movement away from chuck 11. The rods extend between collar 21 and the tube through milled slots on the inside of the collar. Each rod is then attached to the collar by having its end crimped over the edge of clamp portion 21a. Sleeve 21b also helps the welding operation to begin in a manner to be described below.

The end of rods 20 adjacent dead center 14 are connected to plate 22 through turn buckles 23. Each rod is connected to the threaded portion of one of the turn buckles, in any convenient manner. In the embodiment shown, the rods are welded to the turn buckles after which the turn buckles are tightened to place the desired tension in each individual rod.

After the perforated tube with attached spacer rods is mounted for rotation in the engine lathe, wire 25 is wrapped around the tube and rods in a helical coil to form the screen. Means are provided to feed the wire as the perforated tube and rods are rotated. In addition, means are provided for moving the wire feeding means parallel to the axis of rotation of the tube and rods to cause the wire to wrap around the rotating mandrel in helical coils that are spaced the desired distance apart.

In the embodiment shown, the wire feeding means is carried by lathe carriage 16. The means (FIGURE 6) includes wire tensioning and orienting assembly 26, sheave 27, and guide sheave 28. Sheave 27 directs the wire to the mandrel in a direction generally perpendicular to the axis of rotation of the mandrel. Spacer or guide sheave 28 provides the final guidance to the wire as it coils around the mandrel. The orienting and tensioning assembly includes three fixed position rollers 29a, 29b, and 29c. These rollers are mounted in line on plate 30, which is attached to carriage 16 for movement with the carriage along the ways or bed of the lathe. Also mounted on plate 30 are movable rollers 31a and 31b. These rollers are attached to L-shaped brackets 32a and 32b, which are mounted on plate 30 by bolts 34a and 34b. The bolts extend through elongated slots as shown. By loosening bolts 34a and 34b, the L-shaped brackets can be moved to move rollers 31a and 31b varying distances into the space between the permanent rollers. Adjusting screws 33a and 33b extend through the downwardly extending legs of L-shaped brackets 32a and 32b, respectively, and engage the side of plate 30 for adjusting the position of rollers 31a and 31b. The distance rollers 31a and 31b extend below a line tangent with the outside edges of the fixed rollers determines the amount of force required to pull wire 25 through the rollers. Preferably, the surfaces of the rollers are shaped to maintain wire 25 oriented properly for the desired edge of the wire to be placed in contact with the rods to which it is to be welded. The wire is fed to the wire feeding means from a spool (not shown) located adjacent the tail stock end of the lathe.

First or welding electrode 35 is carried by carriage 16 to supply current to wire 25 as it engages each of rods 20 to cause the wire to be welded to the rods. To complete the electrical circuit for the welding current, second or ground electrode 36 is also carried by carriage 16. Both electrodes are disc shaped, mounted for rotation, and positioned to roll along the wire as the wire rotates with the mandrel upon which it is being wrapped. There are only minor differences in the electrodes. Ground electrode 36 is somewhat wider than the welding electrode and has a flat outer surface that rolls along the wire that has already been welded to the mandrel. Welding electrode 35 has a notch or recessed groove 37 in its outer surface, as shown in FIGURE 11. This groove helps guide the wire to the proper position for welding and also limits the distance the electrode can force the wire into the rods, when they are both brought to fusion temperature. For this reason, groove 37 is not as deep as the width of wire 25. This provides clearance 38 when the electrode initially forces the wire against rod 20. As welding current flows from the electrode through the wire into rod 20, the mating surfaces are raised to fusion temperature and the wire will be forced into the rod by the electrode by the amount of clearance 38. As the electrode moves into contact with rod 20, it will transfer the force it is applying to wire 25 to the rod and the wire will not be further forced into the rod. This arrangement helps produce screen with a uniform outside diameter.

A wire that is trapezoidal in cross section is commonly used to make well screens. The narrow side of the wire is positioned to be welded to rods 20. This produces a slot or opening between adjacent coils of wire that widens inwardly. This insures that any material that passes into the slots between the wires can pass to the inside of the screen.

FIGURE 5 is a cross sectional view of the apparatus mounting ground electrode 36 for rotation and for conducting electrical current from the wire to the welding machine to complete the welding circuit. This same assembly is employed to mount welding electrode 35 for rotation and to connect the electrode to the welding machine to receive electrical energy.

Electrode 36 is made of brass or any other suitable material and mounted on shaft 40. The shaft extends into housing 42 and is supported for rotation by roller bearings 41a and 41b. The shaft also electrically connects the electrode with brush 43, which is in sliding contact with the outside surface of the shaft. The brush is attached to the end of brush bar 44, which extends through a lateral opening in housing 42. Brush retaining cap 44a encircles the brush bar and closes the opening. Spring 45 resiliently holds the brush 43 in good electrical contact with shaft 40. Electrical cable 46 connects brush bar 44 to welding machine 47.

To cool the electrode and their associated conductors, while they are in use, shaft 40 is provided with a central opening into which water tube 50 extends. The water tube carries O-ring seal 51 to keep the water from escaping along the outside of the tube. Inner tube 52 extends through the tube into the central opening of shaft 40 well past brush 43. It is connected to water line 53 by connection 53a to provide an outlet for the cooling water. Water is circulated through water line 54, along the outside of inner tube 52, back through tube 52, and out line 53 to carry heat away from the shaft and bushing. Brush 43 is lubricated through lubricant fitting 55.

Welding machine 47 (FIGURE 1) is mounted above carriage 16 for movement with the carriage. The welding machine is carried by horizontal angle irons 47a, which are supported 'by short legs 47b. The latter are extensions of legs 48a-48d, which rest on the carriage. Lateral cross braces 49a and 49b extend between legs 48b and 48d and between 48a and 480, respectively. Electrical current is supplied to the welding machine from an outside source of power (not shown) in the conventional manner. Mounting plate 92 extends between legs 48a and 48b to support transformer 93.

Each electrode, with its associated shaft, shaft housing, etc., is mounted for movement toward and away from the mandrel being wrapped with wire. As best seen in FIGURES 2 and 3, shaft housing 42 of the ground electrode assembly, shown in FIGURE 5, is mounted between spaced arms 56a and 56b. These arms depend from journal 57, which is rotatably supported by shaft 58. The shaft is supported by cross braces 49a and 49b. Housing 59, which supports the Welding electrode shaft, is mounted between arms 61a and 61b, which depend from journal 62. Journal 62 also is supported on shaft 58 for rotation around the axis of the shaft. Thus, each electrode may pivot away from and toward the longitudinal axis of the mandrel.

Preferably, means are provided to hold the electrodes in good electrical contact with the wire, as it is being wrapped on the mandrel. This causes the electrodes to exert lateral forces on the mandrel, as it is rotated, tending to force it to bend. Therefore, means are provided to balance the lateral forces exerted on the mandrel by the electrodes. In the embodiment shown, shaft 65 extends between cross braces 49a and 49b parallel to shaft 58. Depending from shaft 65 are back-up roller support arms '66 and 67' These arms are best seen in FIGURES 2 and 4. Arms 66 and 67 are supported for rotation on shaft 65 by journals 68 and 69, respectively. The arms extend downwardly on the opposite side of the mandrel from the welding electrodes and support back-up rollers 70 and 71. By mounting both the back-up rollers and the electrode so that they can pivot away from and toward the longitudinal axis of the mandrel upon which the wire is being wound, it permits the apparatus to be adjusted for making well screen of various outside diameters. Thus, as shown in FIGURE 2, the electrodes and back-up rollers can be moved into engagement with mandrel A of relatively small diameter, and moved outwardly to engage mandrel B of relatively large diameter.

Means are provided to hold the electrodes and the back-up rollers in engagement with the wire and mandrel. In the embodiment shown, hydraulic cylinder 73 is pivotally mounted between arms 56a and 56b which support the ground electrode assembly. The cylinder is pivotally supported on the arms by stub shafts 73a and 73b that extend laterally from opposite sides of the cylinder. The shafts are rotatably supported in split journals as shown in FIG- URE 2 where a side view of journal 95 is shown. It includes base 95a which is integrally attached to arm 56a and bearing cap 95b.

Piston rod 74 of cylinder 73 is connected to journal 6 bearing 75, which is connected to roller supporting arm 66 by shaft 76. With this arrangement, power cylinder 73 can supply the force desired to hold the electrodes in engagement with the mandrel and this same force will be balanced by the force exerted by the back-up roller. Power cylinder 77 is mounted between 61a and 61b on stub shafts 77a. and 77b in the same manner as is cylinder 73. Its piston rod 78 is connected to back-up roller arm 67 through journal 79 and shaft 80, in the same manner as described above in connection with piston rod 74. Either hydraulic or pneumatic pressure can be used for holding the rollers and electrodes in engagement with the mandrel. Pneumatic pressure has more resiliency and cushion and for that reason is preferred. Whichever is used, the rollers can adjust quickly to changes in the outside diameter of the mandrel upon which the wire is being wrapped.

In operation, the apparatus makes wire screens as follows: The mandrel for the screen, which for purposes of this explanation is made up of perforated tube 13 and elongated spacer rods 20, is mounted between chuck 11 and dead center 14 for rotation around its longitudinal axis. The carriage is moved toward the chuck until welding electrode 35 is adjacent the end of rod holding sleeve 21, as shown in FIGURE 12. This places ground electrode 36 in contact with the outer surface of sleeve 21b. Wire 25 is threaded through the wire tensioning rollers and brought into position adjacent the end of sleeve 21b of split collar 21. Its end is then manually tack welded to one of the spacer rods just past welding electrode 35 to anchor the end of the wire for rotation with the mandrel.

Chuck 11 then starts to rotate the mandrel and carriage 16 is moved longitudinally by the lead screw at the desired rate to space the adjacent coils of wire to form a screen of the desired gage. At the beginning, ground electrode 36 will not be in contact with wire 25. Therefore, the electrical welding circuit is completed from welding electrode 35, through wire 25, into each rod 20, as it passes under the electrode, to collar 21 and then to ground electrode 36. The collar is made of electrically conductive material and good electrical contact is available between the rods and the collar where the rods are crimped over its end surface.

As the carriage travels toward the tail stock of the lathe and the mandrel rotates, additional coils of Wire are wrapped on the mandrel. After two or three coils have been wrapped, the ground electrode will move from the collar into contact with the wire and the wrapping and welding operation will continue for the desired distance down the mandrel with the wire being welded to each spacer rod, as the wire moves with a rod under the welding electrode, in the manner shown in FIGURES 8, 9 and 10. Welding current is supplied continuously to wire 25 by the welding electrode. The electrical current, of course, will take the shortest route between the welding electrode and ground electrode 36. Therefore, as each rod moves under the welding electrode, the welding current will travel through the wire through, into the rod, and along the rod to the coil of wire engaged by the ground electrode. During the time that no welding is occurring, the current will take the shortest path to the ground electrode. The time interval between welds should be as short as possible without reducing the time that is required for the rod to pass under the electrode to the point that the quality of the weld suffers. Generally, the mandrel should be rotated to produce around 1600*1800 welds per minute.

The welding operation produces considerable heat. Therefore, cooling water is directed over the newly formed welds to cool them off as soon as possible, as shown in FIGURE 8, where water lines 97 and 98 direct a stream of water into the newly formed welds. By locating the ground electrode relatively close to the welding electrode, thereby reducing the distance the current has to travel, the amount of current necessary to be provided to perform the welding operation is reduced.

As the carriage moves longitudinally toward the tail stock of the lathe, it carries rod spacing ring 82 with it. As shown in FIGURES 4 and 6, this ring is moved ahead of the welding electrodes and back-up rollers by roller 83 mounted on arm 84. The arm is attached to carriage 16. Roller 83 maintains rolling contact with the ring as it is rotated with the mandrel. A cross sectional view of this spacer ring is shown in FIGURE 7. It comprises an annular ring provided with internal grooves 85, which are designed to receive rods 20. The grooves are located to space the rods equally and to hold them in position to be welded to wire 25, as the wire is wrapped around the rods.

FIGURES 13 and 14 show how wire 25' can be welded directly to perforated tube 13, if a screen without spacer rods 20 is desired. As shown in FIGURE 14, welding electrode 35' would be continuously welding wire 25 to tube 13, as the wire travelled between the electrode and the outside surface of the tube. Ground electrode 36 can follow the welding electrode, rolling on the wire, or since there will be no external rods in this case, it can ride the smooth outside surface of tubular member 13 ahead of the welding electrode.

Means are provided to move the wire feeding means at any desired speed within a given range of speeds to permit the spacing between adjacent coils of wire to be ad justed as desired. FIGURE 15 illustrates the means for accomplishing this in the preferred embodiment. Hydraulic motor 90 is employed to drive chuck 11 through the gear train in lathe head stock 12. Lead screw 18, however, is not driven in the conventional way through the gears in the head stock of the lathe, but through a variable speed transmission 91. This allows the speed of rotation of lead screw 18 to be adjusted independently of the speed of rotation of chuck 11. Thus, the lead screw 18 can be adjusted to move carriage 16 at a speed such that the wire wraps itself on the mandrel to produce a well screen of any desired gage.

From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus and structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. Apparatus for making a well screen by welding together a mandrel comprising an elongated generally tubular structure having lateral flow openings therein and a wire helically wrapped on the mandrel in spaced apart turns, said apparatus comprising a wire feeding means, means for mounting the mandrel and wire feeding means for rotation of the mandrel relative to the wire feeding means and movement of the wire feeding means longitudinally of the mandrel and for feeding wire from said feeding means to and wrapping it on said mandrel in spaced apart helical turns during such rotation and movement, and first and second electrodes movable with said feeding means during such winding, one positioned to engage the exterior of the wire as it is wrapped on the mandrel to supply electrical current to the wire to weld the wire to the mandrel substantially as the wire contacts the mandrel and the other positioned in substantially fixed relation to the first during operation to engage the exterior of at least one turn of wire already welded to the mandrel and spaced from the turn being welded to provide a ground for the welding current supplied by the first electrode with a substantially fixed distance and fixed low resistance current path between electrodes.

2. The apparatus of claim 1 in which the first and second electrodes are disc shaped and mounted for rotation with their outer edges in rolling engagement with the wire.

3. The apparatus of claim 2 further provided with an arm for independently supporting each electrode, said arms being pivotally mounted on the means for mounting the wire feeding means, and means resiliently holding the electrodes in rolling engagement with the wire.

4. The apparatus of claim 3 further provided with two back-up rollers, each positioned on the opposite side of the mandrel from one of the electrodes, two arms, each pivotally mounted on the means for mounting the wire feeding means, with each arm pivotally supporting one of said back-up rollers, and in which said resilient means includes means located between each electrode supporting arm and its oppositely positioned back-up roller supporting arm to independently bias each electrode and its back-up roller toward the mandrel.

References Cited UNITED STATES PATENTS 7/1908 Getty 72140 9/1966 Wilson 144-71 FOREIGN PATENTS 609,805 11/1960 Canada. 

